Examples of single stage turbine wheels having a plurality of radially projecting blades are described in U.S. Pat. Nos. 3,404,867 and 3,923,416. The turbine wheel of U.S. Pat. No. 3,404,867 is constructed of a plurality of coaxial discs each of which has circumferentially spaced concave cut-outs to provide a plurality of arms. The blades in the turbine wheel of U.S. Pat. No. 3,923,416 are in the form of radially projecting wires.